1. Field of the Invention
This invention relates to a rotatory member for fixing for fixing toner image onto a support supporting toner image, and a fixing device having the rotatory member. Particularly, it pertains to a fixing device adapted to supply a mold release agent to a rotatory member for fixing for preventing the off-set phenomenon of toner.
2. Related Background Art
Many heating roller fixing devices have been employed in the art as the fixing device for fixing unfixed toner image onto a support member in image forming devices such as copying machines, electrophotographic printers, etc., and for preventing the off-set phenomenon of toner onto the roller, it has been generally practiced to supply a mold release agent such as silicone oil, etc. to the roller.
Particularly, in full-color image forming device which forms a full-color image by mixing toners with plural different colors, mold releasability of the roller relative to toner is strongly demanded, and therefore a large amount of a mold release agent is supplied to the roller.
Whereas, for the fixing roller to be used for full-color image forming device, not only high mold releasability, but also its elasticity is demanded from aspect of improvement of fixability, and a fixing roller having elastic member layers such as of rubber, etc. laminated is employed. For example, a fixing roller obtained by coating successively a silicone rubber layer, a fluorine rubber layer, a silicone rubber layer coated on the outer peripheral of a core metal such as aluminum, etc. is employed. Among them, the fluorine rubber layer is a layer which functions as the oil barrier layer which prevents penetration of the silicone oil coated on the fixing roller into the silicone rubber layer of the lower layer. Thus, the oil barrier layer prevents particularly swelling of the silicone rubber layer of the lower layer with the silicone oil coated on the fixing roller, thereby preventing breaking of the fixing roller by the influence from heat and pressure.
As described above, the fixing roller to be used for full-color image forming device is coated with a large amount of a silicone oil, but all of the silicone oil coated is not brought away with the recording material during fixing, but a part of the silicone oil remains on the fixing roller. And, the silicone oil remained on the fixing roller moves to both ends of said fixing roller simultaneously with rotation of the fixing roller to flow out into the main image forming device by passing through the journal portions on both ends of the fixing roller, thereby commencing to contaminate internally of the device. Accordingly, as shown in FIG. 1, there has been made an attempt to prevent contamination within the machine with said silicone oil by preventing flow-out of the silicone oil into the main device by forming a mold release agent discharging portion h at the journal portion L of the fixing roller R to block the silicone oil moving to both ends of the fixing roller R and permit it to drop downwardly therefrom.
However, since the core metal made of aluminum and the silicone oil have mutually good wettability with each other and the silicone oil has no repellent force on the core metal, said silicone oil comes over to the mold release agent discharging portion h to reach the end of the journal portion L, further reaching the main device, causing ultimately contamination within the machine to occur similarly as in the prior art.
The present invention has been accomplished in view of the problems as mentioned above.